Complementary metal oxide semiconductor (CMOS) image sensors convert images to electrical signals. Such sensors are found in digital cameras or other electronic devices used for imaging. CMOS image sensors typically use source-followers as isolation devices. In particular, source followers are used to drive analog signals from individual pixel cells to a shared column line. However, the source followers in a pixel array do not all have the same gains, which results in an unbalanced photo response of the CMOS image sensor.